This invention relates generally to cellular communications and applications, and more particularly to a system and method of delivering Time of Arrival (TOA) positioning data for a General Packet Radio Service (GPRS) mobile in a Global System for Mobiles (GSM) communications network.
Wireless telecommunication systems continue to evolve and are currently being deployed in countries throughout the world. There are several types of wireless communication systems currently in service and being deployed including AMPS, D-AMPS, TDMA, CDMA and GSM. These wireless telecommunication systems are currently manufactured by a number of manufacturers, the operation of which are defined by standards groups delegated with the responsibility of ensuring system interoperability. While these various wireless telecommunication systems may have common features, the operability of each is unique.
The Global System for Mobile Communications or GSM, in particular, is one of the newer wireless telecommunication systems being developed and deployed. The GSM system is intended to be widely deployed throughout the world to facilitate reliable wireless telecommunications using one or more GSM standards. The GSM standards continue to evolve, and are currently being discussed and refined to provide for planned services, as well as services to be developed and employed in future generations. Currently, second generation GSM systems are being deployed while third generation (3G) systems are currently under development with planned implementation scheduled for around the year 2000.
In current GSM systems, positioning of a mobile station (MS) is currently provided in limited situations. Specifically, Time Of Arrival (TOA) based positioning has been selected as the mandatory positioning method by the T1P1.5 standards body, requiring an asynchronous intra-cell handover to the same channel during intra-cell handovers. The reason for this is to force the mobile to transmit access bursts to facilitate an intra-cell handover, whereby the time of arrival of the access bursts are measured by surrounding Location Mobile Units (LMUs). These measurements are used in a triangulation process to pinpoint the mobile""s geographical position.
With respect to the General Packet Radio Services (GPRS) class of mobile stations in particular, the intra-cell handover procedure is not suitable as a positioning procedure to locate the geographical position of the mobile. GPRS mobiles don""t have the ability to perform the same Intra-cell handover procedure required in the GSM TOA positioning, and thus a solution facilitating positioning GPRS mobiles is required. The present invention provides for the positioning of GPRS mobiles in a GSM network.
More specifically, according to existing GSM standards, current LMUs cannot distinguish between an access burst generated a GSM mobile versus one generated by a GPRS mobile since, at present, not all LMUs in the network can understand the entire GPRS signaling protocol and thus are not able to communication with GPRS system components. While future deployments are expected to result in LMUs that support the entire GRPS protocol, an interim solution is needed to support interoperability with existing non-GRPS LMUs. As such, a positioning scheme that is able to account for the anticipated mix of both GPRS and non-GPRS LMUs would provide numerous advantages.
The present invention provides a system and method of delivering TOA positioning data for GPRS mobile stations in a GSM network. With the present invention, a complete solution for TOA positioning within the Base Station Subsystem (BSS) centric of the wireless network is provided, allowing signaling between different network components and LMUs that are both GPRS and non-GPRS compatible.
Accordingly, disclosed in one embodiment is a system for positioning a GPRS mobile station in a GSM network by delivering Time of Arrival (TOA) positioning data to a Location Services (LCS) application. The system includes a Gateway GPRS Support Node (GGSN) providing an interface to the LCS application and a Serving GPRS Support Node (SGSN) communicably coupled with the GGSN.
The SGSN is further adapted to communicate with the GPRS mobile station over the GSM network. The SGSN is the node within the GSM network that sends and receives data to and from a GPRS mobile station in the network. In addition, the SGSN keeps track of GPRS mobile stations within its service area. The GGSN, on the other hand, maintains connections with the other networks such as the Internet, X.25 networks or private networks, for example. A GPRS network can use multiple serving nodes, but requires only one gateway node for connecting to an external network such as the Internet.
The system further comprises a Base Station Substation (BSS) serving the GPRS mobile station. The BSS, which includes a Base Transceiver Station (BTS) and a Base Station Controller (BSC), is communicably accessible by the LCS application through the GGSN. A plurality of LMUs are provided and predisposed about the GSM network and configured to deliver TOA positioning coordinates corresponding to an approximate position of the GPRS mobile station. The BSC, as an integral part of the BSS, is configured to select which of the plurality of LMUs are to be used for positioning of the GPRS mobile station. The BSC can be used to determine which of the LMUs are GPRS capable and which of the LMUs are non-GPRS capable. In one embodiment, this information is part of the BSC positioning mechanism meaning that the positioning process is contained almost entirely in the BSS centric.
The system also comprises a Packet Control Unit (PCU) adapted to communicate with the BSS and the LMUs for responding to LCS information requests received through the SGSN. The PCU is further adapted to access the BSC and determine which of the LMUs are GPRS capable and which of the LMUs are non-GPRS capable. In this way, the PCU is able to communicate directly with LMUs which are GPRS capable and indircectly through the BSC with non-GPRS capable LMUs.
According to one embodiment, the PCU is configured to transmit a LOCATION INFORMATION REQUEST messages to the BSC. After receiving a message from the PCU, the BSC sets up a GSM connection to the GPRS mobile station. In the alternative, the BSC can use an existing connection to transfer data to the GPRS mobile station after receiving a POSITIONING REQUEST message from the PCU. Other aspects of the signaling protocol for positioning of the GPRS mobile are shown and illustrated.
During the entire TOA positioning process, the non-GPRS capable LMUs are able to recognize an access burst from the GPRS mobile station. This is accomplished by having the BSC notify the non-GPRS capable LMUs to expect an access burst from the GPRS mobile station. The non-GPRS capable LMUs are configured to manage the access burst sent by the GPRS mobile station.
A technical advantage of the present invention includes the provision of signaling sequences between different network nodes, including the BSS nodes and LMUs, for a complete TOA positioning solution within the BSS centric architecture of a GSM network.
Another technical advantage is the use of non-GPRS capable LMUs for positioning of GPRS mobile stations.
Still another technical advantage is the ability of positioning GPRS mobile stations using newer GPRS-capable LMUs.